Circuit arrangement for preselectors



Dec. 22, 1931.

CIRCUIT ARRANGEMENT FOR PRESELECTORS Filed March 2. 1929 4.5mm muz iuxwHw h hm w M n K E o g a m I "I N h W E 2 m Iuktsm M23 Patented Dec, 22, 1931 I ITE I S A E PA Nr oFFm FRIEDRICH rrtnaor wanna; AUSTRIA, ASSIGNOR T SIEMENS a i GESELLSCHA FT, 0F SIEMENSSTADT, NEAR BERLIN,

' it f ,omonrr gin-nlmenmnnr on rnnsnrlncrons y np plieatioirfiled m r-a 2, 19229; Serial No. 343,894,5ii1di1i Austrian gri l V5, 1 28.

In autornatic telephone exchanges having a single ire-selecting stageoften no signalis provided whereby the calling subscriber I is v notified that he has been switched through 5 to an iinpulserepeater or group selector and that he can coininence to transmit number impulses. This signalecalled exchange signal-isgeher'zrllyinot required ifthe number 7 of group selectors or impulse repeaters be 10 to wait for-the selectonto finish operating even during the hour ofheaviest traffic. Y In the case of automatic private branch exchanges or subexchanges wherein when an outgoing exchange can ijsrnade the subscribers loopisswitchechthroughfdirect to the main exchange, itwould appear desirable to introduce a signal in such exchanges for noti-f 'ng the subscriberthat the preselector or te impulse repeater or group selector has been seized; v t F Asthe general introduction of an exchange signal in existing eirchanges would entail considerableexpen'se,'accordingfto the invention forthe'se subscribers lines pre selectors are used which giyean audible signal (exchange signal), tothe subscriber while'the pre-selector is testing and after'the speaking loop has been switched through to an impulse repeater or group selector or only after the loop has been switchedflthrough to the latter. In thejdrawingFig; 1, there is shown by way of the nsual circuit diagram, one method of carrying out the invention.

"as l Fig, 2 shows a modification of Fig.1 arranged to prevent the application of dial tone the callingline until anidletrunlg-is connected with. J: .o 1 i i Y When the subscriberT takes down receiver, the speakingflooplto the exchange is closed, thereby the calling relay R at the pre selector is operated over earth, winding 1 of the calling relayB, back contact 7, loopof the subscriber T,hack contact-t. :3, resistance Wi 1, battery, earth, Contact?" 11 applies busyhpotential tothe test lead .goin'g'to the finalseleetor, Contact W18 closes the energizing cireuitfor the rotary magnet 1) over: earth, barte back contact/0 17, front contaot comparatively large,.thus preventing having r18, rotary magnet D, relay interrupter earth;

' The rotary inagnet steps the wipersof the V preselector forward until the latter has found a tree line to the repeater, whereupon the" fol;

lowing circuitwis'closed for'the test relay C earth, battery; front Contact i" 14:, windings 1 land 11 ofrelay Q, switch wiper a, resistance 2, earth. Y r

' Contact 6 13 connects upthe cut-off relay over the following circuit: earth, front con tact 0 13, cut ofii relay T, battery, earth; Re lay T is operated and at its contacts t 3 and t7 it disconnects thecalling relay R from the subscribers loop. The closing of the conta'cts c 4 and 10 switches the speaking loop through "to the -irnpnlse repeater. Relay R locks itself inparallel with the relay A att'he repeater earth, battery, relay B, wiper b,

front contact a 4, subscribers loop, front contact c 10,-tvi'per a, relay A, earth, andparallel thereto, winding II ofrelay R, front contact r 8, windingl of relay R earth. Atzthe same timethe contact 7" 9 connectsthe exchan e A signal to the subscribers loop,and he'su h scriberl receives a rattling or buzzing tone as a'signalthat hecan begin the numerical "selection. This signal continues until the subing dialing. r a

The windings of relay R are'given such a resistance that having regard to the resistance of the subscribers loop the relay Aat the re} scriherslloopisopened for the first tirne dure i peater receives suflicientcurrentto be able to operate when shunted by the relay R of the preselector. w i' j The signal can also be connected up in such a inanner that the circuit forthe: hu zze'r or rattle leadiis not'closed until the test relay C has been operated iasjis'shown in Fig. 2.

In that case the exchange signal is appliecl' to the speaking loop after the closing of the oo'ntac'i'c 19, whichis operated by the test e y- 1 What isclainied' isi 1.111 a subsc'ribe'rs line switch, a line 'relay, a switching relay, and a dial'tone circuit' controlled by said relays jointlyQ 2. In asubscribers'line switch, a controlling linerelay, means for maintainingth'e abo 7 said substation, a plurality of trunks, a line switch, meansresponsive when the receiver is lifted at said substation for operating said switch to interconnect said telephone line and an idle one of said trunks, means in said switch controlled by said firstmeans for applying dial tone to the line, and means responsive to the first impulse transmitted over the line for removing the dial tone.

4. In a telephone system, a subscribers substation including an impulse sending device thereat, a line extending from said substation, a line switch, a controlling relay in said switch, means responsive when the receiver is lifted at said substation for operating said relay over a circuit including two conductors of said line in series, means responsive to the operation of said relay for completing a locking circuit for the relay including the calling line loop and for applying dial tone to the line, and means responsive to the first impulse transmitted over the line for opening said locking circuit to deenergize said relay ivhereby the dial tone is removed from the 5. In a telephone system, a subscribers line and a calling device associated therewith, a line switch, a plurality of trunks, means for extending a connection from said line to an idle one of said trunks via said switch, means in the switch effective when a connection has been extended for applying a characteristic tone to the line, and means responsive to the first impulse transmitted by the calling de vice for removing the tone from the line.

6. In a telephone system, a subscribers line equipped with a calling device, a line switch, a controlling relay in said switch, a plurality of trunks accessible to said switch, means responsive to the initiation of a call from said line for operating said relay whereby said switch extends the call to an idle one of said trunks, means responsive to the operation of said relay forcompleting a locking circuit for the relay including the conductors of said line, means responsive to the extension of the call'when said relay is operated for applying a characteristic tone to the line, and means responsive to the momentary opening of the line by the calling device for opening said locking circuit to deenergize said relay and remove the tone from the line.

7 In a telephone system, a line switch for extending a connection from a calling line to an idle trunk, a line relay energized when a call is initiated on the line, a cut off relay energized when the call is extended to an idle trunk, means responsive when both said relays are energized for applying a char acteristic tone to the line, and means responsive to a momentary interruption of the line for deenergizing said line relay whereby the tone is removed from the line.

8. In a non-numerical hunting switch terminating a line and having access to a group of trunks, a line relay, a circuit for initially operating said relay to cause said switch to hunt for and connect with an idle one of said trunks, means for opening said circuit responsive to the trunk being connected with, a holding circuit for maintaining the relay operated after said first circuit is opened, and means controlled by said relay for applying a characteristic tone to the line.

' 9. In a non-numerical hunting switch terminating a line and having access to a group of trunks, a linerelay, a circuit for initially operating said relayto cause the switch to hunt for and connect with an idle one of said trunks, means for opening said circuit responsive to the trunk being connected with, a holding circuit completed responsive to the operation of said relay for maintaining the relay operated after said first circuit is opened, and contacts on said relay for con necting a characteristic tone to the line.

10; In a non-numerical hunting switch terminating a line and having access to a group of trunks, a line relay, a circuit for initially operating said relay'to cause the switch to hunt for and connect with an idle one of said trunks, means for opening said circuit responsive to the trunk being connected with, a holding circuit including contacts of said relay for maintaining the relay operated after said first circuit is opened, means controlled by said relay for connecting a characteristic tone to the line, and means responsive to a momentary interruption of said holding circuit for deenergizing said relay to disable said holding circuit and to disconnect said tone from the line.

11. In a non-numerical hunting switch for connecting a calling line with an idle trunk, a line relay operated over the calling line loop to start the hunting operation of the switch responsive to the initiation of a call, a switching relay operated to connect the line through to a selected trunk and to open the original energizing circuit of the line relay, a locking circuit including the calling line'loop and contacts on the line relay for maintaining the line relay operated after its energizing circuit is opene and contacts on the line relay for connecting a tone to the line.

12. In a telephone system, a line, a nonnumerical hunting switch for connecting said line with an idle trunk, a line relay and a switching relay for the switch, means responsive to a call. on the line for operating said line relay over a circuit including the calling line loop and contacts of the switching relay 7 to initiate the hunting operation of the switch, means for operating the switching relay to connect the line through toan idle trunk and to open the circuit of the line relay, a holding circuit including the calling line loop and contacts on the line relay for maintaining the line relay operated independent of said first circuit, and a source of tone connected to said holding circuit.

13. In an automatic switch having access to a group of trunks, a double-wound line relay energized initially over a circuit including one winding of the relay anda' calling suhscriloers line loop, means responsive to the energization of said relay for operating the switch to hunt for and connect with an idle one of said trunks, means responsive to effecting the connection With said trunk for opening the initial energizing circuit of said relay and for completing a holding circuit ina cluding the two windings of the relay in series and the calling line loop, and means responsive to a momentary interruption of the calling line loop for disabling said holding circuit for the duration of the connection.

In witness whereof, I hereunto subscribe my name this 30th day of'January, A. D. 1929. r i a FRIEDRICH LILL. 

